1. Field of the Invention
This invention relates to a process for producing water-insoluble polymers and, more particularly, to a process for producing a water-insoluble polymer of uniform shape having a desired geometric form.
2. Description of the Prior Art
Conventionally, the production of water-insoluble polymers of uniform size and shape having a desired geometric form from water-soluble, radical-polymerizable monomers and crosslinkable monomers having two or more radical-polymerizable vinyl groups involved several problems concerning formability, variation in shape, controllability of the polymerization reaction, and the like. Thus, its utilization for industrial purposes was very difficult.
In the prior art, suspension polymerization has been used to produce water-insoluble polymers, especially in particulate form, from monomers as described above. According to this process, an aqueous solution of monomers and a surface active agent are added to a medium in which water and the monomers are completely or substantially insoluble. This mixture is vigorously agitated to disperse the aqueous solution of monomers in the form of fine droplets. Then, a polymerization initiator which is easily soluble in the monomers is added to the suspension, whereby polymerization is effected to produce a water-insoluble polymer in particulate form. The particle diameter of the water-insoluble polymer produced by this prior art process depends on the type of medium, monomers, and surface active agent used, the shape of the reactor, and the shape and speed of the agitator. However, this process is normally suitable for the production of a water-insoluble polymer in the form of fine particles having a diameter of 0.1 mm or less. Moreover, the resulting water-insoluble polymer exhibits such a wide particle diameter distribution that it must be sieved if a particulate polymer having a preselected range of particle diameters is desired. The particulate polymer fraction having undesired particle diameters are usually discarded, which makes this process uneconomical. Furthermore, it is extremely difficult to utilize this process in the production of a particulate polymer having a large particle diameter of several millimeters or greater. In this case, it frequently happens that large polymer masses are formed to foul the inner walls of the reactor and thereby force the discontinuance of the operation. Still another disadvantage of suspension polymerization is that it cannot produce a water-insoluble polymer having a geometric form other than the particulate one.